1. Field of the Invention
The present invention relates to a method for producing a gas barrier laminate film and a gas barrier laminate film which can be obtained by the method. The present invention relates to, in particular, a method for producing a gas barrier laminated film suitably used for image display devices using a flexible support such as an organic electroluminescence device (henceforth referred to as “organic EL device”) and liquid crystal display device and a gas barrier laminated film which can be obtained by the method.
2. Description of the Background
With the wide spread of personal computers and portable information terminals, the demand for a thin and light electronic display is rapidly increasing. Glass substrates are mainly used in the liquid crystal display devices, which are currently most widely spread, and the organic EL devices, which draw attentions because of its high visibility due to the self-coloring property. However, in view of production of lighter devices, impact resistance, flexibility thereof and so forth, use of flexible plastic substrates as the substrates of liquid crystal display devices and organic EL devices is preferred.
However, plastic substrates have poorer heat resistance and poorer gas barrier property compared with glass substrates. Therefore, they are unsuitable for forming high definition patterns and also suffer from disadvantage of poor durability.
To improve such drawbacks of plastic substrates as described above, various researches have been reported so far. For example, a gas barrier laminate film of which gas barrier property is improved by adding a layered compound to a plastic substrate is known as described in, for example, Japanese Patent Laid-open Publication (KOKAI) No. 2001-205743 (claims 1 to 5, page 3, paragraph [0013] to page 4, paragraph [0022]). However, the gas barrier property of the gas barrier laminate film described in the patent document is insufficient, and further improvement has been desired.
Further, also reported is a gas barrier laminate film of which gas barrier property is improved by coating an organic-inorganic hybrid film using the so-called sol-gel method, in which a metal alkoxysilane is hydrolyzed with an acid or base catalyst and then condensed by dehydration to obtain a metal oxide, as described in, for example, Japanese Patent Laid-open Publication (KOKAI) No. 2000-323273 (page 6, paragraph [0059] to page 7, paragraph [0061]), Japanese Patent Laid-open Publication (KOKAI) No. 2001-277443 (page 2, paragraph [0012] to page 6, paragraph [0056]), and Japanese Patent Laid-open Publication (KOKAI) No. 2000-71396 (page 3, paragraph [0011] to page 6, paragraph [0037]). In the improved gas barrier laminate films described in these patent documents, the amount of the acid catalyst used for the hydrolysis during the formation of the hybrid film is not definitely described, or it is a small amount, i.e., 0.05 molar equivalent or less with respect to the amount of the added alkoxysilane.
When an acid catalyst is used in the aforementioned sol-gel method, the amount of the acid catalyst is generally in the range of 0.0001 to 0.01 molar equivalent with respect to the amount of the added alkoxysilane, as described in, for example, Sakuhana, S., “Science of Sol-gel Method”, pp. 17-53, Agune Shofu-sha, published on Aug. 20, 2001. This is because, as described in the document, if the amount of the acid catalyst is increased, metal oxide particles having a large size become likely to be produced, and as a result, produced is a film having a large pore size, which is unsuitable for the production of satisfactory gas barrier laminate films. Therefore, the addition amount of acid catalyst is within the aforementioned range in all of the improved gas barrier laminate films of the above patent documents. Thus, there is a problem that the gas barrier property of the organic-inorganic hybrid film itself in the improved gas barrier laminated films cannot be considered sufficient.
Furthermore, examples of use of an acidic cation exchange resin as the hydrolysis catalyst is also reported in, for example, Japanese Patent Laid-open Publication (KOKAI) No. 2002-60525 (page 3, paragraph [0020], page 4, paragraph [0025] to paragraph [0035]). If an acidic cation exchange resin is used as described in this patent document, there may be caused a reaction similar to that caused with an acid catalyst used at a locally high concentration. However, the reaction time of the reaction caused between the solid phase and liquid phase is prolonged, and moreover, a heterogeneous reaction system is used. Therefore, the method suffers from a drawback that a film exhibiting sufficiently uniform and high gas barrier property cannot be obtained.